The present invention generally relates to an apparatus and method for forming an image, and is capable of being applied to an image forming apparatus and method, which utilize toner of a copying machine or printer having a photosensitive drum.
In an image forming apparatus and method utilizing toner, there is carried out an image forming process for electrifying minus charges on the surface of a photosensitive drum, exposing (varying the surface potential of) the photosensitive drum to laser beams based on picture signals to form a latent image, causing it to absorb minus charged toner to form a visible image, and transferring and fixing the visible image on a paper.
In such image formation, a toner (which will be hereinafter referred to as a xe2x80x9crecovered tonerxe2x80x9d) which has been already utilized in image formation, and a toner (which will be hereinafter referred to as a xe2x80x9cnew tonerxe2x80x9d) which has not yet been utilized in image formation, are mixed to be utilized. That is, the recovered toner is recycled to be used.
Conventionally, as a method for recycling a recovered toner, there is a method for conveying a recovered toner, which leaves a cleaner auger, to a developing device by means of a connecting auger, which connects the cleaner auger to the developing device, and returning the recovered toner directly into the developing device.
In this method, the rotation of the cleaner auger must be in synchronism with the rotation of the photosensitive drum, and the rotation of the connecting auger to the developing device must be connected with the cleaner auger. In some operation modes, these conditions are not satisfied, so that the recovered toner recovered by the cleaner is fixed to components and so forth in the cleaner auger and/or connecting auger without being fed.
If the body cover of the coping machine or printer is open and closed in such a state, the large amount of the recovered toner fixed to the auger(s) and/or the inner walls of pipes in the cleaner and/or connecting auger are conveyed into the developing device at a time by vibrations occurring during the opening/closing of the cover. For that reason, the developer toner specific concentration is temporarily in a high state (an excessive toner state), so that image fogging occurs on an image transferred to a paper.
That is, an external additive is peeled from the recovered toner, and paper powder is mixed in the recovered toner. Therefore, even if the recovered toner is supplied into the developing device, the rise of the quantity of electrification is worse than that in the case of the new toner, and if the percentage of the recovered toner increases, image fogging is easy to occur.
Also, during adjustment for carrying out initialization after exchanging the developer on the basis of the toner empty display when the new toner is completely consumed, the supply of the recovered toner from the cleaner part to the developing device continues, so that the percentage of the recovered toner in the developing device increases. Also in this case, as described above, the developer toner specific concentration is in the high state (the excessive toner state), so that image fogging occurs on an image transferred to a paper.
It is an object of the present invention to prevent conventional bad influences which are caused when a recovered toner is excessively supplied into a developing device.
In order to accomplish the aforementioned object, according to the present invention, an image forming apparatus comprises: recovered toner housing means for temporarily storing therein a recovered toner; a connecting/conveying device for conveying the recovered toner from a cleaner part to the recovered toner housing means; recovered toner supply means for supplying the recovered toner, which is housed in the recovered toner housing means, to a developing device; new toner housing means for housing therein a new toner; new toner supply means for supplying the new toner, which is stored in the new toner housing means, to the developing device; toner concentration ratio detecting means for detecting a toner concentration ratio in the developing device; and control means for controlling the recovered toner supply means and the new toner supply means in accordance with the contents detected by the toner concentration ratio detecting means, to supply the recovered toner and new toner to the developing device, wherein the control means causes the amount of the recovered toner to be supplied to be less than the amount of the recovered toner during a usual operation, which is determined in accordance with the contents detected by the toner concentration ratio detecting means, or stops the supply of the recovered toner, while a predetermined period condition is satisfied after the occurrence of a predetermined event in which the amount of the recovered toner stored in the recovered toner housing means is temporarily excessive.
In order to accomplish the aforementioned object, according to the present invention, there is provided an image forming method for causing a connecting/conveying device to convey a recovered toner from a cleaner part to recovered toner housing means to house therein the recovered toner, and causing control means to control recovered toner supply means and new toner supply means in accordance with a toner concentration ratio in a developing device, which is detected by toner concentration ratio detecting means, to supply the recovered toner, which is stored in the recovered toner housing means, and a new toner, which is stored in new toner housing means, to the developing device, wherein the control means causes the amount of the recovered toner to be supplied to be less than the amount of the recovered toner during a usual operation, which is determined in accordance with the contents detected by the toner concentration ratio detecting means, or stops the supply of the recovered toner, while a predetermined period condition is satisfied after the occurrence of a predetermined event in which the amount of the recovered toner stored in the recovered toner housing means is temporarily excessive.